Phospholipids: The conversion of phospholipids into lysophospholipids in the gastric mucosa of control animals and animals undergoing ulcerogenesis will be studied. Thus far surface active lipids refluxing from the duodenum have been studied with reference to weakening of the gastric mucosal barrier. We propose to investigate phospholipase activity in the gastric mucosa proper and the generation of lysphospholipids in situ with the idea that surface active lipids may possibly be generated in significant amounts in the gastric mucosa. Glycolipids: Preliminary evidence (Slomiany, Slomiany and Horowitz, Studies on Changes in Lipid Profiles of the Rat Gastric Mucosa with Stress Ulcers; Clin. Chim. Acta, in press) indicates a change in the profile of glycolipids of the rat gastric mucosa undergoing ulcerogenesis. The ulcerated mucosa contains less polyhexosyl ceramides than the normal. We are attempting to learn whether there are differences in the glycolipids secreted by the stomach as compared to those which are present in the mucosa. Histamine-stimulated gastric juice from the rat and dog will be analyzed for glycolipid variety and quantity. It is possible that secretion of glycolipid may serve as an indicator of membrane shedding or loss.